A carrier aggregation (CA) technology is supported by a time division duplex (TDD) standard in a Long Term Evolution (LTE) system, namely, an LTE TDD system. Multiple component carriers or serving cells may be simultaneously allocated to one user equipment (UE) to support transmission at a high data rate.
In the prior art, a maximum of five carriers or serving cells may be configured for one UE. However, if a configuration of a carrier or serving cell is an uplink-downlink configuration 5, transmission of acknowledgement information is limited. For example, for a transmission mode of a physical uplink control channel (PUCCH) format 3, a maximum quantity of bits in acknowledgement information supported by this transmission mode is 20. In the prior art, in a carrier aggregation scenario, when there is one carrier in some TDD uplink-downlink configurations or the carrier is in some reference uplink-downlink configurations, a maximum of two carriers can be configured for the UE. In addition, in some TDD reference configurations, acknowledgement information corresponding to all downlink subframes of a secondary serving cell is fed back in one or several uplink subframes. As a result, a feedback delay is increased, and feedback performance is degraded.